1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a semiconductor memory device including one-time programmable (OTP) memory cells.
2. Description of the Related Art
A semiconductor memory device is a storage device which stores data and reads the data when the data is needed. The semiconductor memory device is generally divided into two categories: a random access memory (RAM) and a read only memory (ROM). The ROM is a nonvolatile memory which can retain data even if power is off. The ROM includes a programmable read only memory (PROM), an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM), a flash memory device, etc. The RAM is a volatile memory which cannot retain data when power is off. The RAM includes a dynamic random access memory (DRAM), a static random access memory (SRAM), etc. Aside from these memory devices, an innovative semiconductor memory device using nonvolatile materials instead of capacitors used in a DRAM has been developed. The innovative semiconductor memory device includes a ferroelectric random access memory (FRAM) using ferroelectric capacitors, or a magnetic random access memory (MRAM) using a tunneling magneto-resistive (TMR) layer.
One time programmable (OTP) cells can be programmed only one time. A memory block including OTP memory cells is typically used for storing trimming integrated circuit information, security identification information, chip identification information, calibration data, or storing main memory block redundancy information. As systems including integrated circuits become more technologically sophisticated or operationally complex, a memory block including OTP memory cells requires a higher operation speed.